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British architects and timber building specialists have hailed plans by a Japanese company to build a 350m-tall mainly wooden tower – but questioned the need for such buildings in future

Timber supplier Sumitomo Forestry this month revealed plans to create the 70-storey skyscraper on a site in Tokyo, to mark the firm’s 350th anniversary in 2041.

Designed in conjunction with architects at Nikken Sekkei, the structure would use 185,000m3 of timber and cost an estimated 600 billion yen (£4 billion).

It would be 90 per cent made from wooden materials, using a ‘braced tube’ structure that sees steel frame vibration control braces positioned inside a column and beam structure made from a combination of wood and steel.

Structural Timber Association board member Nic Clark told the AJ it was a ‘very exciting project’.

‘The benefits of using timber in construction are obvious in terms of speed, weight, carbon sequestration and aesthetic,’ he added.

Clark said elements of steel or concrete had to be considered for high-rise wooden schemes. ‘This way you can see a project like this being entirely possible in the UK.’

Founding director Anthony Thistleton-Smith said the Tokyo proposal was ‘positive’.

‘Projects like this demonstrating the far reaches of timber’s potential should surely convince all clients that mass timber is part of a new normal to be appraised on every site,’ he said.

‘We would hope that in a few decades, given the pace of innovation so far, it will truly be possible to build such a large structure predominantly in timber without having to load it up with concrete and steel, which add embodied carbon and compromise the natural flexibility of timber structures, which is essential in earthquake zones.’

However, Thistleton-Smith questioned whether the prototype would be followed by a sustained programme of timber towers.

‘In 24 years, will a 350m-tall building be the answer to sustainable living in the city, regardless of what it is made from?’

‘The sky’s the limit for the fast-evolving world of modern timber construction techniques, and the architectonic expression of new materials and forms remains underexplored,’ said de Rijke.

But he added: ‘The relevant question is not how high can you go, but do you really need towers to achieve urban density?

‘’The considered answer to this century’s architecture is not the tallest timber tower but clever composite structures as well as new high-density six to twelve storey building typologies.

‘Mixing in but reducing steel and concrete to the absolute minimum, while exploiting timber’s unique ability to invert the construction industry paradigm for carbon production, pollution and waste, is the desired future.’

However, Sumitomo has big plans for wooden towers.

’We will make every effort to further enhance fire and seismic resistance as well as durability; thoroughly reduce construction costs; develop new materials and construction methods; and develop trees that will be used as resources,’ the company said.

’We will strive to create environmentally-friendly and timber utilising cities to change cities into forests.’

Readers' comments (2)

If a concrete block of flats such as Grenfell can kill 81 in a fire, what would happen if these timber blocks catch fire.
And it is not always about whether the technical difficulties have been solved, fire resistance, spread of flame, charring etc, but more whether poor performance on site (Ronan Point) or poor quality cost engineering (Grenfell) can be overcome.
Anyway, as both Thistleton-Smith and Alex de Rijke both suggest, low rise can achieve good city density.

I agree with comment above; to me this is very much a case of the dog walking on its hind legs.
I would rather wait to see new technology in intumescent coatings for timber, with seriously high specifications; or the use of larger timber profiles which can char enough to protect the structural core.
I have seen multi-storey timber kit buildings become immediate infernoes; imagine if timber-structured buildings became the norm, you would have a Grenfell every couple of months, fire-breaks or no fore-breaks.
A lot of lessons were learned in the Great Fire of London, might need to be re-learned.

If architects are designing timber buildings for 'sustainability''s sake or even just for fun, then that's bad design in my book.

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